High-power ultracapacitor energy storage pack and method of use

ABSTRACT

An ultracapacitor energy storage cell pack includes an ultracapacitor assembly including a plurality of parallel ultracapacitors and balancing resistors in series; an enclosure for the ultracapacitor assembly; a controller; one or more temperature sensors; a pack voltage sensor; a GFI sensor; one or more cooling fans carried by the enclosure; an on/off relay coupled to the ultracapacitor assembly and the controller, the on/off relay activated by the controller during normal operation of the ultracapacitor assembly and deactivated by the controller when the GFI sensor detects a ground fault interrupt condition, the one or more temperature sensors detect an over-temperature condition, or the pack voltage sensor detects an over-voltage condition; and a pre-charge resistor and a pre-charge relay coupled to the ultracapacitor assembly and the controller, and activated by the controller to cause the pre-charge resistor to limit pack charge current until the ultracapacitor assembly reaches a minimum voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application is a continuation-in-part application ofU.S. patent application Ser. No. 09/972,085 filed Oct. 4, 2001.

FIELD OF THE INVENTION

[0002] The field of the invention relates to a high-voltage, high-powerultracapacitor energy storage pack composed of a large number ofserially connected individual low-voltage ultracapacitor cells thatstore an electrical charge.

BACKGROUND OF THE INVENTION

[0003] The connecting together of individual battery cells forhigh-voltage, high-energy applications is well known. However, thechemical reaction that occurs internal to a battery during charging anddischarging typically limits deep-cycle battery life to hundreds ofcharge/discharge cycles. This characteristic means that the battery packhas to be replaced at a high cost one or more times during the life of ahybrid-electric or all-electric vehicle. Batteries are somewhatpower-limited because the chemical reaction therein limits the rate atwhich batteries can accept energy during charging and supply energyduring discharging. In a hybrid-electric vehicle application, batterypower limitations restrict the drive system efficiency in capturingbraking energy through regeneration and supplying power foracceleration.

[0004] Ultracapacitors are attractive because they can be connectedtogether, similar to batteries, for high-voltage applications; have anextended life of hundreds of thousands of charge/discharge cycles; andcan accept and supply much higher power than similar battery packs.Although ultracapacitors are typically more expensive than battery packsfor the same applications and cannot store as much energy as batterypacks, ultracapacitor packs are projected to last the life of thevehicle and offer better fuel-efficient operation through brakingregeneration energy capture and supplying of vehicle acceleration power.

[0005] During charging and discharging operation of the ultracapacitors,parasitic effects cause the cell temperature to increase. Cooling isrequired to minimize increased temperature operation that would degradethe energy storage and useful life of each ultracapacitor.

[0006] Low-voltage energy cells, batteries, or ultracapacitors areconnected in series to obtain high-voltage energy storage. Because ofvariations in materials and manufacturing, energy storage cells are notperfectly matched. As the serially connected pack operates throughmultiple charge and discharge cycles, the cell differences cause theenergy storage to become more and more imbalanced among the cells. Theenergy storage imbalance from cell to cell limits the performance of theoverall pack and can shorten the life of the individual cells.

[0007] Packs of batteries and packs of ultracapacitors have been builtin various forms and configurations. Various different wiring harnesses,buss bars, and connections have been used for current routing andvoltage monitoring. Various different types of circuits for charging,discharging, and equalizing have also been built. Energy storage cellshave been mounted in various “egg crate” or “wine rack” style verticaland horizontal support structures. High-voltage packages containbatteries enclosed within a single pack. Batteries have even beenconnected together by simply touching under some pressure the positiveend of one battery against the negative end of another battery such ascan be found in flashlights, small toys and appliances. High-energypacks usually include some form of convection air or liquid cooling.

SUMMARY OF THE INVENTION

[0008] The present invention involves an ultracapacitor high-energystorage pack with structural support, environmental protection,automatic cooling, electrical interconnection of the ultracapacitors,remote ON/OFF switching, a safety pre-charge circuit, a safety andautomatic equalizing discharge circuit, a programmable logic controller,a digital interface to a control area data network for control andstatus reporting, and an optional fire sensing and suppression system.The pack is ideal for high-voltage, high-power applications of electricand hybrid-electric vehicle propulsion systems, fixed site high-powerload averaging, and high-power impulse requirements. The pack is housedin an aluminum box enclosure with a detachable access lid. The inside ofthe box has a thick anti corrosion, electrically insulating coating. Thebox has holes cut out for the mounting of cooling fans, air intakes, andelectrical connections. The air intake cutouts have provision formounting external replaceable air filters that can be serviced withoutopening the box. Mounted to the interior of the box are aluminum guidesupport strips for three plastic support plates. Plastic, as anon-conductive material, provides for the safe operation of thehigh-voltage connections. Two of the plastic plates have wine rack holecutouts that form the support structure for individual cylindricalultracapacitor cans and the third plastic plate has pre mounted bussbars and smaller holes for fastening bolts. The first two plastic platesstructurally support and separate the ultracapacitors to provide spacefor cooling airflow along the direction of the plates. The third platesupports and positions the cans by the threaded end terminals that arebolted to the plate. Buss bars are fastened to the inside of the thirdplate to provide connections between adjacent rows of ultracapacitors.The cans, which are arranged in rows of three, are electrically andstructurally connected together with threaded studs and buss bars.

[0009] In a preferred embodiment, the triple can connections arearranged four rows deep and twelve rows along the top to efficientlypackage one-hundred and forty four (144) cylindrically shapedultracapacitor cans with threaded polarized connections at each end ofthe can. For different design requirements, the longitudinal dimensionof the box may be shortened or lengthened to respectively delete or addone or more layers of twelve (12) ultracapacitors. Similarly, the depthdimension of the box may be shortened or lengthened to respectivelydelete or add a layer of thirty-six (36) ultracapacitors. Againsimilarly, the width dimension of the box may be shortened or lengthenedto respectively delete or add a layer of forty-eight (48)ultracapacitors.

[0010] In addition to the ultracapacitors, the box houses and hasmounting provision for other electrical components. Temperature sensorsand controllers switch the forced-air cooling fans on and off forthermal management of the ultracapacitor environment. A pre-chargeresistor is automatically switched in series with the power chargecircuit when first turned on to prevent overloading the charging energysource. High-power relays called contactors provide remote controlledswitching of the energy storage pack into and out of the charge and loadcircuits. An integral Control Area Network (CAN) controller is connectedto multiple pin electronics connectors to report status parameters andcontrol the switching of the energy storage pack through a CAN digitaldata network. The pack also contains integral Ground Fault Interrupter(GFI) and fire sensing automatic safety shutoff systems.

[0011] Finally, a balancing or drain resistor is mounted in parallelaround each ultracapacitor to safely discharge the pack to an inactivestate over a period of time. This periodic discharge function alsoserves to equalize all the ultracapacitors energy storage to a balancedcondition.

[0012] A further aspect of the invention involves an ultracapacitorenergy storage cell pack including an ultracapacitor assembly having aplurality of parallel ultracapacitors and balancing resistors in series,each balancing resistor in parallel with each ultracapacitor toautomatically discharge each ultracapacitor over time, thereby balancingthe ultracapacitors of the ultracapacitor assembly; an enclosure toenclose and protect the ultracapacitor assembly; a controller for theultracapacitor assembly; one or more temperature sensors to monitortemperature of the ultracapacitor assembly and coupled to thecontroller; a pack voltage sensor to monitor voltage of theultracapacitor assembly and coupled to the controller; a GFI sensor tomonitor for a ground fault interrupt condition of the ultracapacitorassembly and coupled to the controller; one or more cooling fans carriedby the enclosure and controlled by the controller to cool theultracapacitor assembly based upon temperature sensed by the one or moretemperature sensors; an on/off relay coupled to the ultracapacitorassembly and the controller, the on/off relay activated by thecontroller during normal operation of the ultracapacitor assembly anddeactivated by the controller when the GFI sensor detects a ground faultinterrupt condition, when the one or more temperature sensors detect anover-temperature condition, or when the pack voltage sensor detects anover-voltage condition; and a pre-charge resistor and a pre-charge relaycoupled to the ultracapacitor assembly and the controller, thepre-charge relay activated by the controller to cause the pre-chargeresistor to limit pack charge current until the ultracapacitor assemblyreaches a minimum voltage.

[0013] Another aspect of the invention involves a method of using anultracapacitor energy storage cell pack including the steps of providingan ultracapacitor energy storage cell pack including a ultracapacitorassembly having a plurality of parallel ultracapacitors and balancingresistor in series, each balancing resistor in parallel with eachultracapacitor to automatically discharge each ultracapacitor over time,thereby balancing the ultracapacitors of the ultracapacitor assembly andassuring a safe condition for service personnel; an enclosure to encloseand protect the ultracapacitor assembly; a controller for theultracapacitor assembly; one or more temperature sensors to monitortemperature of the ultracapacitor assembly and coupled to thecontroller; a pack voltage sensor to monitor voltage of theultracapacitor assembly and coupled to the controller; a GFI sensor tomonitor for a ground fault interrupt condition of the ultracapacitorassembly and coupled to the controller; one or more cooling fans carriedby the enclosure and controlled by the controller to cool theultracapacitor assembly based upon temperature sensed by the one or moretemperature sensors; an on/off relay coupled to the ultracapacitorassembly and the controller, the on/off relay activated by thecontroller during normal operation of the ultracapacitor assembly anddeactivated by the controller when the GFI sensor detects a ground faultinterrupt condition, when the one or more temperature sensors detect anover-temperature condition, or when the pack voltage sensor detects anover-voltage condition; and a pre-charge resistor and a pre-charge relaycoupled to the ultracapacitor assembly and the controller, thepre-charge relay activated by the controller to cause the pre-chargeresistor to limit pack charge current until the ultracapacitor assemblyreaches a minimum voltage; automatically discharging the ultracapacitorsof the ultracapacitor energy storage cell with the balancing resistorsto balance ultracapacitors of the ultracapacitor assembly and assure asafe condition for service personnel; cooling the ultracapacitorassembly with the one or more cooling fans based upon temperature sensedby the one or more temperature sensors; activating the on/off relay withthe controller during normal operation of the ultracapacitor assemblyand deactivating the on/off relay with the controller when the GFIsensor detects a ground fault interrupt condition, when the one or moretemperature sensors detect an over-temperature condition, or when thepack voltage sensor detects an over-voltage condition; and activatingthe pre-charge relay with the controller to cause the pre-chargeresistor to limit pack charge current until the ultracapacitor assemblyreaches a minimum voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which are incorporated in and form apart of this specification, illustrate embodiments of the invention andtogether with the description, serve to explain the principles of thisinvention.

[0015]FIG. 1 is an exploded perspective view drawing of an embodiment ofa half module of an ultracapacitor energy storage cell pack.

[0016]FIG. 2 is a perspective view of an embodiment of an ultracapacitorenergy

[0017]FIG. 3 is a top plan view of an embodiment of a circuit board forthe half module illustrated in FIG. 1 and ultracapacitor energy storagecell pack illustrated in FIG. 2.

[0018]FIG. 4 is an exploded perspective view of an alternativeembodiment of a ultracapacitor energy storage cell pack.

[0019]FIG. 5 is an exploded perspective view of the ultracapacitors andsupport plates of the ultracapacitor energy storage cell pack of FIG. 4.

[0020]FIG. 6 is perspective detail view taken of detail 6 of theultracapacitors, threaded interconnections between the ultracapacitors,and parallel drain resistors mounted with ring terminals of theultracapacitor energy storage cell pack of FIG. 5.

[0021]FIG. 7 is a side-elevational view of an embodiment of a middlesupport plate of the ultracapacitor energy storage cell pack illustratedin FIG. 4, and the middle support plate is shown with cutouts for theultracapacitors and the drain resistors.

[0022]FIG. 8 is a side-elevational view of an embodiment of an endsupport plate of the ultracapacitor energy storage cell pack illustratedin FIG. 4, and the end support plate is shown with cutouts for themounting bolts and the support guide mounting rivets.

[0023]FIG. 9 is a block diagram of the ultracapacitor energy storagecell pack illustrated in FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] With reference to FIGS. 1 and 2, an embodiment of anultracapacitor energy storage cell pack 10 will now be described. FIG. 1illustrates an exploded view of an embodiment of a half module 15 of theultracapacitor energy storage cell pack 10. FIG. 2 illustrates anembodiment of an assembled ultracapacitor energy storage cell packmodule 10, which includes two half modules 15 fastened together.Although each half module 15 preferably includes eighty ultracapacitors20, each half module may have other numbers of ultracapacitors 20.Further, the ultracapacitor pack 10 may have other numbers of modules 15besides a pair (e.g., 1, 3, 4, etc.).

[0025] The ultracapacitor pack 10 is shown in exploded view in FIG. 1 toillustrate the different levels in the half module 15 that are addedduring assembly of the half module 15. Each of these levels will now bedescribed in turn below followed by a description of the assemblyprocess.

[0026] An aluminum base plate 25 forms a bottom or inner-most level ofthe half module 15. The base plate 25 includes a welded frame 30 aroundedges of the base plate 25.

[0027] A polycarbonate crate plate 35 is seated inside the frame 30 andincludes cutouts or holes 40 with a shape that matches the cross-sectionof the ultracapacitors 20. The base plate 25 and crate cutouts 40 forman x, y, and z location and mounting support for the ultracapacitors 20.The cutouts 40 also prevent the ultracapacitors 20 from rotating duringuse, e.g., mobile vehicle use.

[0028] In the embodiment shown, the individual ultracapacitors 20 have ageneral square-can shape (i.e., rectangular parallelpiped). Thecross-section of the ultracapacitors 20 is 2.38 in. by 2.38 in. and thelength is about 6 in. On an upper-most or outer-most end of theultracapacitor 20, two threaded lug terminals 45 and a dielectric pastefill port 50 protrude from an insulated cover 55 of the ultracapacitor20. The cover 55 of the ultracapacitor may include a well encircled by aprotruding rim. Shrink plastic that normally surrounds sides or exteriorcapacitor casing 60 of the ultracapacitor 20 is removed to better exposethe exterior casing 60 to circulated cooling

[0029] A box frame 65 ties together the base plate 25 and frame 30 withcircuit boards 70, and a top polycarbonate cover 75. The box frame 65has elongated lateral cutouts 80 on two opposing sides to provide forcross-flow air cooling. Bottom flanges 85 provide a mounting surface totie two of these box frames 65, and, hence, two half modules 15,together to form the single ultracapacitor pack module 10 shown in FIG.2. The box frame 65 includes a large upper rectangular opening and alarge lower rectangular opening.

[0030] The next layer is a first ¼ in. foam rubber insulating andsealing sheet 90 that covers the ultracapacitors 20. The first sheet 90has cutouts for the ultracapacitor terminals 45 and fill port 50 so thatthe sheet 90 can seal tightly against the cover 55 of the ultracapacitor20.

[0031] A second ⅛ in. foam rubber insulating and sealing sheet 95 may beplaced on top of the previous first sheet 90. The second sheet 95includes rectangular cutouts or holes 100. The cutouts 100 receivecopper bar electrical interconnections 105. The cutouts 100 in the sheet95 simplify the assembly and proper placement of the copper barelectrical interconnections 105. The sheet 95 also seals the copper barelectrical interconnections 105. The copper bar electricalinterconnections 105 include holes that the ultracapacitor terminals 45protrude through.

[0032] Two identical main circuit boards 70 (e.g., 40-ultracapacitormain circuit boards) may lay on top of the foam rubber sheets 90, 95.With reference additionally to FIG. 3, each main circuit board 70 mayinclude holes 107 that the ultracapacitor terminals 45 protrude through.In the embodiment shown, each circuit board 70 may have mounting holes107 for 40 (8 by 5) ultracapacitors less two corner positions requiredfor frame structure mounting. Instead of two circuit boards 70, a singlecircuit board 70 may be used. Thus, as used herein, the word “circuitboard” means one or more circuit boards. Fasteners such as lug nutsfasten the individual ultracapacitor terminals 45 and copper bars 105 tothe circuit boards 70 and compress the foam rubber sheets 90, 95 inbetween the cover 55 of the ultracapacitor 20 and the circuit boards 70.Thus, the circuit board 70 forms the location and mechanical support aswell as the electrical connections for the ultracapacitors 20. The foamsheets 90, 95 seal around the rim of the ultracapacitor terminals 45. Aprocessor and display circuit board mounts on top of the main circuitboard 70.

[0033] Although the ultracapacitor pack 10 and the half modules 15 areshown as being generally rectangular in shape, either or both may haveshapes other than generally rectangular such as, but not by way oflimitation, circular, oval, other curvilinear shapes, other rectilinearshapes, and other polygonal shapes.

[0034] A top aluminum frame 110 and the transparent polycarbonate cover75 may attach to the frame structure to complete the half module 15. Thetransparent cover 75 allows observation of a light emitting diode (LED)failure detection display that indicates the active/inactive status ofthe ultracapacitors 20.

[0035] Together, the bottom base plate 25, crate plate 35, box frame 65,sealing sheets 90, 95, and circuit board(s) 70, and ultracapacitorterminal fasteners form an ultracapacitor mounting assembly 112 for theultracapacitors 20. The ultracapacitor mounting assembly 112 provides amounting surface for the copper bar interconnects 105, maintains theposition and spacing of the ultracapacitors 20 in the X, Y, and Zdirections, does not allow the ultracapacitors to rotate when connected,and the main circuit board(s) 70 provides a mounting platform for thecell equalization, failure detection, processor, and LED displaysystems. Attaching the ultracapacitors 20 to the mounting assembly 112by the terminals 45 instead of the exterior ultracapacitor casing 60allows the ultracapacitors 20 to be more effectively cooled because themajority of the surface area of the ultracapacitors 20 is in the coolingair stream supplied by the cross-flow air cooling assembly 115. Sealingalong the cover 55 and around the terminals 45 protects the terminals 45from water, dust, and other contaminants.

[0036] An exemplary method of assembling the ultracapacitor half module15 will now be described. The ultracapacitors 20 are first placed ontothe bottom base plate 25, with the bottoms of the ultracapacitors 20extending through the square cutouts 40 of the crate plate 35. The boxframe 65 is applied over the ultracapacitors 20, so that theultracapacitors extend through the large lower and upper rectangularopenings of the box frame 65. The ¼ in. foam rubber insulating andsealing sheet 90 is placed on top of the ultracapacitors 20, with theultracapacitor terminals 45 and fill port 50 protruding through cutoutsin the sheet 90. The ⅛ in. foam rubber insulating and sealing sheet 95is placed on top of the previous sheet 90 and the copper bar electricalinterconnections 105 are placed into the rectangular cutouts 100 of thesheet 95. The ultracapacitor terminals 45 also protrude through holes inthe copper bar electrical interconnections 105. The main circuit boards70 are layered on top of the foam rubber sheets 90, 95 so that thethreaded ultracapacitor terminals 45 protrude through the correspondingholes in the circuit boards 70. Lug nuts are screwed onto the threadedterminals 45, compressing the foam rubber sheets 90, 95 in between thecover 55 of the ultracapacitor 20 and the circuit boards 70, andsecuring the ultracapacitors 20 and copper bars 105 in position. Theprocessor and display circuit board is mounted on top of the maincircuit board 70. The top aluminum frame 110 and the transparentpolycarbonate cover 75 are placed over the circuit boards and attachedto the frame structure to complete the half module 15. A pair of halfmodules 15 may be positioned back to back (i.e., facing oppositedirections with the bottoms of the aluminum base plates 25 touching) anda cross-flow air cooling assembly 115 may be attached to the framestructure, adjacent the elongated lateral cutouts 80 on one side of thebox frames 65. The half modules 15 may be bolted or otherwise fastenedtogether at the respective bottom flanges 85 to complete theultracapacitor pack module 10.

[0037] To determine if one or more ultracapacitors 20 in the pack 10need to be replaced, a user observes the light emitting diode (LED)failure detection display through the transparent cover 75. The LEDfailure detection display includes an array of LEDs that correspond tothe array of ultracapacitors 20, each LED indicating the status of acorresponding ultracapacitor 20. Each unlit LED indicates acorresponding failed LED. An ultracapacitor 20 in the pack 10 canquickly and easily be replaced by simply unfastening the frame andunbolting only the failed ultracapacitor 20 that had been previouslyidentified by the LED display. The replacement ultracapacitor is putinto position and the procedure reversed.

[0038] With reference to FIGS. 4-9, and initially, FIGS. 4 and 5, anultracapacitor energy storage cell pack (hereinafter “ultracapacitorpack) 200 constructed in accordance with another embodiment of theinvention will now be described. The ultracapacitor pack 200 includes aultracapacitor cell and winerack support assembly (hereinafter“ultracapacitor assembly”) 210, an ultracapacitor pack box enclosure(hereinafter “box enclosure”) 220, a metal lid 230, an air filterbracket 240 (w/air filter), cooling fans 250, fan finger guards 260,higher-power precharge resistor 270, Programmable Logic Controllermodule (hereinafter “PLC”) 280, high power relays (kilovac contactors)290, electrical connectors 300, 310, 320 and other discrete componentsmounted within the box enclosure 220.

[0039] The ultracapacitor assembly 210 includes one-hundred andforty-four (144) ultracapacitors 330 connected in series to provide anominal 360 volts DC, 325 watt-hours energy storage. The value of eachultracapacitor 330 is 2600. Farads. In alternative embodiments, theultracapacitor assembly 210 may have other numbers of ultracapacitors,different types of ultracapacitors, and/or an overall different amountof voltage and/or power. Each ultracapacitor 330 is connected with aparallel drain resistor 340 (FIG. 6). The ultracapacitor assembly 210includes a first wine rack middle support plate 350, a similar secondwine rack middle support plate 360, and a wine rack end support plate370 for supporting the ultracapacitors 330.

[0040] The box enclosure 220 is preferably made of metal and includessquare end cutouts 380 in rear wall 382 to accommodate air flowtherethrough and circular cutouts 390 in front wall 392 to accommodatethe cooling fans 250. The front wall 392 and rear wall 382 are joined byopposite parallel side walls 394. The filter(s) of the air filterbracket 240 is externally serviceable and fits over the square cutouts380 of the rear wall 382. The interior of the box enclosure 220 andunderside of the lid 230 is coated with a thick material that provideselectrical insulation and corrosion protection as an additional level ofsafety for the box enclosure 220. The inner bottom of the box enclosure220 includes support plate guides for mounting the wine rack middlesupport plates 350, 360 and end support plate 370.

[0041]FIG. 5 shows an exploded view of the ultracapacitor assembly 210.The ultracapacitors 330 are cylindrical canisters with aluminum femalethreaded connections at each end, which receive male threaded aluminuminterconnection studs 400 for connecting the ultracapacitors 330 inseries. Aluminum bus bars 410 and aluminum interconnection washers arealso used to interconnect the ultracapacitors 330 in series at the endsof the rows. Providing electrical connections made of aluminum metalprevents any corrosive galvanic effects from dissimilar metals.Additionally, the threaded connections are covered with a silicondielectric grease to prohibit environmentally caused corrosion.

[0042] The wine rack middle support plates 350, 360 and end supportplate 370 are made of nonconductive plastic material to prevent anyhigh-voltage arcing or other high-voltage leakage effects that couldoccur over time due to vibration and shock. The wine rack middle supportplates 350, 360 and end support plate 370 are different in constructionto allow ease of assembly and replacement of any canister row.

[0043] With reference to FIG. 7, the wine rack middle support plates350, 360 include a pattern of generally circular cutouts 430 forreceiving the ultracapacitors 330. The cutouts 430 include an additionalsemi-circular recess 440 to accommodate and support the drain resistors340. The drain resistors 340 are preformed with ring terminals 442 (FIG.6) attached to leads of the drain resistors 340 for simplicity ofmounting and electrical connection. Additional semi-circular recesses450 along a top edge 460 and bottom edge 470 of the wine rack middlesupport plates 350, 360 provide clearance for the attaching rivets ofsupport guides on a bottom of box enclosure 220 and the lid 230. Thewine rack middle support plates 350, 360 are made of {fraction (3/16)}″thick polycarbonate plastic for strength and electrical insulation.

[0044] With reference to FIG. 8, the wine rack end support plate 370includes a pattern of circular holes 480 for receiving threaded boltfasteners for mounting the ultracapacitors 330. Additional semi-circularrecesses 490 along a top edge 500 and a bottom edge 510 of the wine rackend support plate 370 provide clearance for the attaching rivets ofsupport guides on a bottom of the box enclosure 220 and the lid 230. Thewine rack end support plate 370 is made of {fraction (3/16)}″ thickGrade G-10/FR4 Garolite glass fabric laminate with an epoxy resin thatabsorbs virtually no water and holds its shape well. Inside-mountedaluminum bus bars 410 are affixed in place to the wine rack end supportplate 370 with silicon RTV (Room Temperature Vulcanizing, which is acommon jelly-like paste that cures to a rubbery substance used invarious applications as adhesive and/or sealer). The bus bars 410 arepre-positioned to avoid confusion that could cause assembly mistakes.

[0045]FIG. 9 is a general block diagram of the ultracapacitor pack 200.As indicated above, each ultracapacitor 330 is connected in parallelwith the drain resistor 340. One-hundred and forty-four (144) of theseparallel connections are connected in series to provide a nominal 360volts DC, 325 watt-hours energy storage. The value of eachultracapacitor 330 is 2600. Farads and the value and power of the drainresistor 340 is selected to completely discharge the ultracapacitor 330over a number of hours during an inactive period of the ultracapacitorpack 200. The energy drain action is slow enough so as not to interferewith the normal operation of the ultracapacitor pack 200. The dischargeis also slow enough so as not to cause any significant temperatureincrease from the drain resistors 340 within the ultracapacitor pack200. The chemical composition of the ultracapacitor 330 allows charge tobuild up across the ultracapacitor 330 over a period of time after theultracapacitor 330 is shorted and left open. The drain resistors 340allow a safe discharge of the high voltage of the ultracapacitor pack200 to eliminate any shock danger from the ultracapacitor “memory” topersonnel servicing the ultracapacitor pack 200.

[0046] Because the ultracapacitors 330 can accept hundreds of amperes ofelectrical current during charging, a connection to an energy sourcewould appear as a short circuit to the energy source. To accommodatethis problem, a high-power pre-charge resistor 270 with its own heatsink is mounted inside the box enclosure 220 and used to limit theinitial charging current. Based on input to a pack voltage sensor 520,the PLC 280 controls a pre-charge contactor relay 540 to engage thepre-charge resistor 270 until the ultracapacitors 330 reach a minimumsafe voltage level.

[0047] The PLC 280 is the control center for additional features.Through a Control Area Network (CAN) bus interface (e.g., SAE standardJ1939), the PLC 280 offers remote ON/OFF control and status reportingof: the control relay positions for on/off relay 550 and precharge relay540, pack voltage sensor 520, ground fault interrupt (GFI) sensor 560,cooling fans 250, box temperature sensor 570, over temperature sensor580, optional fire sensor 590, and optional fire suppression system 600.The PLC 280 also uses input from the box temperature sensor 570 to turnon and off the cooling fans 250. During normal operation of theultracapacitor pack, the on/off relay 550 is activated. The on/off relay550 is deactivated by the PLC 280 when the GFI sensor 560 detects aground fault interrupt condition, when the over temperature sensor 580detects an over-temperature condition, or the pack voltage sensor 520detects an over-voltage condition. The fire suppression system 600 isactivated by the PLC 280 in the event a fire condition is detected bythe fire sensor 590 to extinguish any fire in the ultracapacitor pack200. A 360 VDC+stud feed thru 610 is an external power cable attachmentfor the positive side of the ultracapacitor pack 200. A 360 VDC− studfeed thru 620 is an external power cable attachment for the negativeside of the ultracapacitor pack 200. A 24 VDC+, 24 VDC− power connector630 provides the positive and negative dc power connections for the PLC280. A digital data interface connector 640 includes the wires thatconnect to the CAN buss network and is also the port by which the PLC280 is programmed.

[0048] The ultracapacitor pack 200 includes structural support,environmental protection, automatic cooling, electrical interconnectionof the ultracapacitors, remote ON/OFF switching, a safety pre-chargecircuit, a safety and automatic equalizing discharge circuit, aprogrammable logic controller, a digital interface to a control areadata network for control and status reporting, and an optional firesensing and suppression system. The pack is ideal for high-voltage,high-power applications of electric and hybrid-electric vehiclepropulsion systems, fixed site high-power load averaging, and high-powerimpulse requirements.

[0049] While embodiments and applications of this invention have beenshown and described, it would be apparent to those in the field thatmany more modifications are possible without departing from theinventive concepts herein. The invention, therefore, is not to berestricted except in the spirit of the appended claims.

What is claimed is:
 1. An ultracapacitor energy storage cell pack,comprising: an ultracapacitor assembly including a plurality of parallelultracapacitors and balancing resistors in series, each balancingresistor in parallel with each ultracapacitor to automatically dischargeeach ultracapacitor over time, thereby balancing the ultracapacitors ofthe ultracapacitor assembly; an enclosure to enclose and protect theultracapacitor assembly; a controller for the ultracapacitor assembly;one or more temperature sensors to monitor temperature of theultracapacitor assembly and coupled to the controller; a pack voltagesensor to monitor voltage of the ultracapacitor assembly and coupled tothe controller; a GFI sensor to monitor for a ground fault interruptcondition of the ultracapacitor assembly and coupled to the controller;one or more cooling fans carried by the enclosure and controlled by thecontroller to cool the ultracapacitor assembly based upon temperaturesensed by the one or more temperature sensors; an on/off relay coupledto the ultracapacitor assembly and the controller, the on/off relayactivated by the controller during normal operation of theultracapacitor assembly and deactivated by the controller when the GFIsensor detects a ground fault interrupt condition, when the one or moretemperature sensors detect an over-temperature condition, or when thepack voltage sensor detects an over-voltage condition; and a pre-chargeresistor and a pre-charge relay coupled to the ultracapacitor assemblyand the controller, the pre-charge relay activated by the controller tocause the pre-charge resistor to limit pack charge current until theultracapacitor assembly reaches a minimum voltage.
 2. The ultracapacitorenergy storage cell pack of claim 1, wherein the controller is aprogrammable logic controller with a digital data interface to an SAEstandard J1939 Control Area Network (CAN).
 3. The ultracapacitor energystorage cell pack of claim 1, wherein the ultracapacitor energy storagecell pack stores up to a nominal 325 watt-hours of electrical energy atup to a nominal 360 volts DC.
 4. The ultracapacitor energy storage cellpack of claim 1, wherein the enclosure includes an inside with ananti-corrosion and electrical insulation coating thereon.
 5. Theultracapacitor energy storage cell pack of claim 1, wherein theultracapacitor assembly includes two polycarbonate wine rack middleplate supports with cutouts that receive the ultracapacitors andbalancing resistors.
 6. The ultracapacitor energy storage cell pack ofclaim 1, wherein the ultracapacitor assembly includes a wine rack endsupport plate made of a glass fabric laminate with an epoxy resin, andhas a pattern of holes for mounting the ultracapacitors.
 7. Theultracapacitor energy storage cell pack of claim 1, wherein the one ormore cooling fans include two cooling fans, the enclosure includes afront wall with two circular cutouts to accommodate the two coolingfans, and the ultracapacitor energy storage cell pack further includestwo finger guards covering the two respective cooling fans.
 8. Theultracapacitor energy storage cell pack of claim 7, wherein theenclosure includes a front wall with a plurality of openings therein toallowing incoming airflow therethrough, and the ultracapacitor energystorage cell pack further includes an externally serviceable filtermounted over the plurality of openings of the front wall.
 9. Theultracapacitor energy storage cell pack of claim 1, wherein theultracapacitors are mechanically and electrically interconnected withaluminum connections.
 10. The ultracapacitor energy storage cell pack ofclaim 1, further including a fire sensor and a fire suppressionsubsystem activated by the controller upon a fire indication input fromthe fire sensor.
 11. A method of using an ultracapacitor energy storagecell pack, comprising: providing an ultracapacitor energy storage cellpack including a ultracapacitor assembly having a plurality of parallelultracapacitors and balancing resistor in series, each balancingresistor in parallel with each ultracapacitor to automatically dischargeeach ultracapacitor over time, thereby balancing the ultracapacitors ofthe ultracapacitor assembly and assuring a safe condition for servicepersonnel; an enclosure to enclose and protect the ultracapacitorassembly; a controller for the ultracapacitor assembly; one or moretemperature sensors to monitor temperature of the ultracapacitorassembly and coupled to the controller; a pack voltage sensor to monitorvoltage of the ultracapacitor assembly and coupled to the controller; aGFI sensor to monitor for a ground fault interrupt condition of theultracapacitor assembly and coupled to the controller; one or morecooling fans carried by the enclosure and controlled by the controllerto cool the ultracapacitor assembly based upon temperature sensed by theone or more temperature sensors; an on/off relay coupled to theultracapacitor assembly and the controller, the on/off relay activatedby the controller during normal operation of the ultracapacitor assemblyand deactivated by the controller when the GFI sensor detects a groundfault interrupt condition, when the one or more temperature sensorsdetect an over-temperature condition, or when the pack voltage sensordetects an over-voltage condition; and a pre-charge resistor and apre-charge relay coupled to the ultracapacitor assembly and thecontroller, the pre-charge relay activated by the controller to causethe pre-charge resistor to limit pack charge current until theultracapacitor assembly reaches a minimum voltage; automaticallydischarging the ultracapacitors of the ultracapacitor energy storagecell with the balancing resistors to balance ultracapacitors of theultracapacitor assembly and assure a safe condition for servicepersonnel; cooling the ultracapacitor assembly with the one or morecooling fans based upon temperature sensed by the one or moretemperature sensors; activating the on/off relay with the controllerduring normal operation of the ultracapacitor assembly and deactivatingthe on/off relay with the controller when the GFI sensor detects aground fault interrupt condition, when the one or more temperaturesensors detect an over-temperature condition, or when the pack voltagesensor detects an over-voltage condition; activating the pre-chargerelay with the controller to cause the pre-charge resistor to limit packcharge current until the ultracapacitor assembly reaches a minimumvoltage.
 12. The method of claim 11, wherein the controller is aprogrammable logic controller with a digital data interface to an SAEstandard J1939 Control Area Network (CAN).
 13. The method of claim 11,wherein the ultracapacitor energy storage cell pack stores up to anominal 325 watt-hours of electrical energy at up to a nominal 360 voltsDC.
 14. The method of claim 11, wherein the enclosure includes an insidewith an anti-corrosion and electrical insulation coating thereon. 15.The method of claim 11, wherein the ultracapacitor assembly includes twopolycarbonate wine rack middle plate supports with cutouts that receivethe ultracapacitors and balancing resistors.
 16. The method of claim 11,wherein the ultracapacitor assembly includes a wine rack end supportplate made of a glass fabric laminate with an epoxy resin, and has apattern of holes for mounting the ultracapacitors.
 17. The method ofclaim 11, wherein the one or more cooling fans include two cooling fans,the enclosure includes a front wall with two circular cutouts toaccommodate the two cooling fans, and the ultracapacitor energy storagecell pack further includes two finger guards covering the two respectivecooling fans.
 18. The method of claim 17, wherein the enclosure includesa front wall with a plurality of openings therein to allowing incomingairflow therethrough, and the ultracapacitor energy storage cell packfurther includes an externally serviceable filter mounted over theplurality of openings of the front wall.
 19. The method of claim 11,wherein the ultracapacitors are mechanically and electricallyinterconnected with aluminum connections.
 20. The method of claim 11,further including a fire sensor and a fire suppression subsystemactivated by the controller upon a fire indication input from the firesensor.